Most digital data processing (computer) systems include at least one printing system to produce printed records of data that has been interchanged and generated by other elements of the computer system. A typical printing system comprises a single, stand-alone printer designed to sequentially accept printing requests from the computer system it is connected to, and to process these requests in order to produce a printed copy of the information processed by the computer system. The printer may have a small memory which stores information necessary to process the print requests.
Over the years, computer systems have become very sophisticated. Some digital data processing computers include a very large, very fast processor. Other digital data processing computer systems include a number of processors that are connected together to form a cluster or network. Both types of systems are capable of processing large amounts of data very rapidly. As a result, modern digital data processing systems generate a large number of printing requests to produce the required hard copy records of the data they process.
The increased number of printing requests has created new demands on printing systems. For instance, most printing systems are unable to process printing requests as fast as they are received. This creates a back-up, as printing clients wait to have their printing requests acknowledged and serviced. To date, the response to this situation has been to provide high speed printers that are capable of processing printing requests at a rapid rate, and to provide computer systems with multiple printers so that a number of printing requests may be serviced simultaneously.
A disadvantage of the current way multiple printers are connected to a computer system is that each printer can only service printing requests from one processor or one group of processors. In some instances one printer may stand idle if it does not have any printing requests to service, while an adjacent printer, connected to a different group of processors, has a line or queue of unprocessed printing requests to service. In other words, the way multiple printers currently are attached to computer systems, they are unable to load balance the printing requests they receive, and as a result there is an inefficient use the printers' services.
Also, printers currently being provided for computer systems have substantially greater capabilities than printers previously supplied. This is because the previous printers had keys which impacted on the paper to produce the desired image; the capabilities of these printers were limited by the type and number of keys they had. Currently, computer systems include non-impact printers such as laser printers and ink jet printers. Non-impact printers are able to produce an almost unlimited variety of alphanumeric characters, symbols, figurative and image representations on paper. Furthermore, the next generation of printers will be able to produce printed copy in an array of colors.
Current printers, particularly non-impact printers, require resources in order to produce the desired print copy. The resources are generally divided into two categories, namely, fonts and forms. Fonts are the instructions needed to produce specific characters and symbols on the paper. Forms include instructions directing where the characters should be placed on the paper. Some printers are also capable of using different hardware features to process different printing requests. These hardware features include such things as using paper from different trays for different printing requests, (i.e. from a tray filled with blank paper or one filled with letterhead paper depending on the destination of the printed copy, or based on different trays having different sizes paper in them), which output tray the printed copy should be deposited in, or if the printed copy should be deposited in the tray face up or face down. In an accounting environment, for example, form information may direct how a set of figures and descriptive text is displayed on a page, font information may direct the size and shape of the specific numbers and text, and printing instructions may direct from which tray paper is supplied to the printer in order to service the printing request.
The increased demand on printing systems has also made it necessary to provide individual printing systems with large amounts of resources. Different resources are regularly required by a printing system to service different printing requests. For instance, in a network environment, a first printing client may want the printing system to produce scientific output in tabular or figurative form and a subsequent printing client may want the printing system to produce a business letter. In this situation, the separate printing requests would require different resources. Moreover, color printers require additional resources which include the instructions necessary to produce color copy.
Problems arise because a printing system can usually only store a limited amount of resources. If a printing client wants a printing request processed that needs resources that the printing system does not have, it must send those resources along with the printing request or the request will not be satisfactorily serviced. A printing system can be provided with large amounts of storage space for resources; however, doing so substantially increases the cost of the printing system in order to provide resources that may be seldom, if ever, used. Thus, a printing system is usually limited in the types of printing requests it services, or the printing clients themselves must take the time to forward resources to the printing system in order to have more unusual printing requests serviced. In either situation, the overall efficiency of the digital data processing system is reduced.
Another consideration with a printing system is the system's ability to report its own status to other parts of the data processing system. For instance, after a printing client has generated a printing request for a printing system, it may later check on the request's status; i.e., whether the request was processed. Also, printing systems occasionally need to call attention to their own condition. For example if a printer runs out of paper, it may need to report to the printing clients that it is temporarily unable to process their printing requests, and to an operator who may be at a remote location that it needs attention. Currently, most printing systems are unable to do more than activate a local signal, such as flashing lights, to indicate their status. This has made it difficult to place printers at remote locations, such as at an office work station, since personnel who would be nearby but not immediately around the printer, for example, personnel at adjacent work stations, would not be made that the printer requires attention.